ambisonic.net - where surround-sound comes to life.
BBC Research and Development - Projects - Ambisonics and Periphony. Exploring Ambisonics' audio format capabilities in 3D surround sound
Room EQ Wizard - registration required, donations encouraged but otherwise free. Acoustic Measurement and Analysis REW is a Java application for measuring room acoustics and analysing room and loudspeaker responses. It includes tools for generating test signals; measuring SPL and impedance; measuring frequency and impulse responses; generating phase, group delay and spectral decay plots, waterfalls, spectrograms and energy-time curves; generating real time analyser (RTA) plots; calculating reverberation times; calculating Thiele-Small parameters; determining the frequencies and decay times of modal resonances; displaying equaliser responses and automatically adjusting the settings of parametric equalisers to counter the effects of room modes and adjust responses to match a target curve.
VST plugins written by Dave Malham and Ambrose Field from the Department of Music, University of York. England. Public domain.